The invention relates generally to an improved strand fabricating machine; also known in the art as a braiding machine.
More specifically, the invention relates to an apparatus for the control of moving strands from rotating strand supply bobbins.
Still further, the invention relates to the control of relative strand movement, without significantly affecting or altering strand tension, on a braiding machine with two sets of carriers for a strand supply bobbin being rotated in opposite directions and being generally axially aligned, as a set of front and rear strand carriers and supply bobbins. The multiple sets of contra-rotating front and rear strands are let-off from the supply bobbins under controlled tension. The moving sets of strands are interwoven, rear strands over and around front strands, by guiding of the rear strands through an arc segment relative to the central axis of the braiding machine. The arcuate movement does not change or substantially alter rear strand length thereby maintaining strand tension. The tensioned interwoven sets of strands are led to and around a circular ring in front of the front bobbins which has an effective diameter coincident with the rotational axis of the front bobbins. The circular ring may be rotated in the same direction as the moving set of strands from the rear supply bobbins to eliminate any rotational friction or "drag back" of the rear strands. Then, the interwoven strands are pulled from the braiding machine to a "work center" for tight braiding around a core or mandrel moving along the central axis of the machine.
In the prior art, the use of positively actuated lever or arm means for interweaving sets of moving strands between the braiding point and sets of contra-rotating strand supply bobbins is disclosed in: U.S. Pat. No. 447,262, 1891, Tregurtha, et al; U.S. Pat. No. 814,711, 1906, Larsson; U.S. Pat. No. 1,516,568, 1924, Horn; U.S. Pat. No. 1,689,389, 1928, Horn; U.S. Pat. No. 1,864,249, 1932, Horn; U.S. Pat. No. 1,955,206, 1934, Standish; U.S. Pat. No. 3,834,271, 1974, Hinds, et al; U.S. Pat. No. 3,892,161, 1975, Sokol; U.S. Pat. No. 4,034,642, 1977, Iannucci, et al; and, U.S. Pat. No. 4,372,191, 1983, Iannucci, et al.
In the prior art, the use of axially located circular rings for peripheral and guiding engagement with moving strands from contra-rotating sets of upper-lower strand supply bobbins is disclosed in: U.S. Pat. No. 814,711, 1906, Larsson; U.S. Pat. No. 851,204, 1907, Parks & Wardwell; and, U.S. Pat. No. 1,704,888, 1929, Frederickson.
So far is is known to the inventors, the most relevant prior art patent is U.S. Pat. No. 814,711, 1906, Larsson. This patent discloses a braiding machine having a set of lower carriers G for a strand supply bobbin 1 mounted on an annular body D for rotation in one direction. A set of upper carriers L for a strand supply bobbin 2 are movable around the upper side of the annular body D in a raceway H. The upper carriers L are rotated in an opposite direction to the lower carriers G by a series of spur pinions m interconnecting rack-teeth j on bases i for the carriers L with a large spur gear-wheel d. The gear-wheel is rotated around a standard A by a power shaft B through a spur-pinion f which meshes with a spur gear-wheel C, which carries the gear wheel-d. The carriers, L and G, are generally axially aligned so that the orbits or paths of movements of the lower and upper sets of bobbins, 1 and 2, "are of about equal diameter." (page 2, col. 1, 11. 31-34)
The apparatus according to the invention is used with a braiding machine having a set of rear carriers mounted on the rear side of a first table for rotation in one direction, and a set of front carriers mounted on and driven around the front side of the first table, by rotation of a second table in front of the first table, in the opposite direction. This braiding machine also has a central axis stationary shaft for rotatable mounting of the first and second tables thereon.
In Larsson, the annular body D has a set of peripheral radial slots v which intersect the raceway H for the upper carriers L. In the apparatus according to the invention, the first table has a set of peripheral and radially arcuate slots.
In Larsson, the set of moving strands from the lower bobbins 1 pass through a set of elongated guides or carriers J positioned within the radial slots v in the annular body D and mounted for swinging movements in vertical planes radial to the axis of the braiding machine. In the apparatus according to the invention, the set of moving strands from the rear bobbins is guided by a set of swing arms movable in a common plane perpendicular to the axis of the braiding machine. Each swing arm is carried on the first table between two of the radially arcuate slots and has an eyelet engaging a rear strand prior to movement thereof into a first table radially arcuate slot. The rear strands are guided through an arc segment relative to the central axis of the braiding machine, by the movement of the swing arms perpendicular to the braiding machine axis.
In Larsson, the pivotally mounted thread-carriers or strand guides J are actuated by a set of rotating cams p "formed with two concentric portions and two working portions, so there will be `dwells` in the motions of the thread carrier while it is in its inward and its outward positions, and the abruptness of the working portions are such that the thread-carrier will be swung in the radial slot v, which intersects the raceway for the upper set of bobbin-carriers between the times when such carriers reach and are passing across said slots, also the thread-carriers and the upper set of bobbin-carriers with their bobbins, will dodge each other at the said slotted portions v of the annular part D." (page 3, col. 1, 11. 51-64)
In Larsson, the lobed cams p for swinging movement of the strand guide J are driven by a spur-pinion r carried by a shaft q which meshes with a small pinion u carried by an axis-shaft m.sup.2 carried by every other one of the pinions m driven by the large spurgear-wheel d.
In the apparatus according to the invention, the braiding machine has a control element positioned around the central axis stationary shaft and behind the rear side of the first table. The control element carries and positions a stationary cam track radially inwardly of a set of rear strand supply bobbins. The cam track has a set of alternating inner and outer portions providing a "dwell" in movement for all of the strand guiding mechanisms during rotation of the first table.
In Larsson, a circular ring formed by elements kk.sup.2 k.sup.3 and termed as the "cap" is supported as an extension of the upstanding tubular portion a of the base or standard A. "As shown, the periphery of the thread-supporting cap is in substantial vertical alinement with the path of movement of the upper set of bobbins. By this construction all of the threads have a common support concentric to the point where the braid is formed." (page 2, col. 1, 11. 47-53). As understood by the inventors, the stationary circular braid ring of Larsson is intended to secure uniform braiding at the "work center", even though the set of moving strands from the lower bobbins 1 are being swung by the carriers J, back and forth or in and out, in vertical planes radial to the axis of the braiding machine. Larsson intends that the "cap lies in proximity to the bobbins, thereby forming a sharp angle between the threads when the thread-carriers are in their extremes of movements to prevent any liability of a tangle forming." (page 2, col. 1, 11. 64-65, col. 2, 11. 1-3)
In the apparatus according to the invention, a circular braid ring is mounted coaxially on the central axis stationary shaft in front of the second table and also has an outer diameter coincident with the axes of rotation of the front bobbins. The inventors intend that the circular braid ring function to extend the "braid point" of the braiding machine, as far as practical toward infinity. As shown by reference to drawing FIG. 6, the circular braid ring defines the forward apex of a conical envelope generated by the linear and arcuate movement of the rear tensioned strands so that uniform and concentric braiding with the linearly moving tensioned front stands will occur at the braid ring outer diameter. The braiding or interweaving of the strand sets is achieved within the parameters of the braiding machine and subsequent movement of the interwoven strands from the braiding machine to a "work center" is merely for tightening of an established braid configuration around a core or mandrel moving along the central axis of the machine.